I am a young man with a successful business all praise be to Allaah The Almighty. I am careful to discharge my duties regarding this money, paying what is due upon me. I also have a surplus which I use to give charity to a number of Muslim families in the form of a monthly allowance, now it became a basic source of income for them. A mosque is being built in my neighborhood. Is it preferable to devote the surplus of money I have to the construction of this mosque or to continue helping these fellow Muslims?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhiwasallam, is His slave and messenger.

Allaah The Almighty Urged us to build mosques. He Says (what means): {[Such niches are] in mosques which Allaah has ordered to be raised and that His name be mentioned therein.} [Quran 24:36]

And the Prophet, sallallaahu ‘alayhiwasallam, said in the Hadeeth: “Whoever builds a mosque, Allaah The Almighty Will Build a similar one to it for him in the Paradise.” [Muslim]

Our Lord also Urged us to give charity to the poor and needy, particularly when they are in a pressing need for financial help.

Allaah The Exalted Says (what means):{But he has not broken through the difficult pass. And what can make you know what is [breaking through] the difficult pass? It is the freeing of a slave; or feeding on a day of severe hunger; an orphan of near relationship; or a needy person in misery.}[Quran 90:11-16]

Moreover, the self-restraining poor are more entitled to charity than beggars.

In a Hadeeth narrated on the authority of IbnMas‘ood the Prophet, sallallaahu ‘alayhiwasallam, said: "The truly poor one is not the that  who constantly walk from person to person and  is satisfied with one or two morsels or one or two dates." I ( the companion ) said: "Who are thetruly  poor one, O Messenger of Allaah?" He said: "it is he who neither begs people nor finds what is suficient to his needs.  Moreover, people do not recognize his state so that they give him charity." [Ahmad]

Given the above, is it better to give charity to the poor or to build a mosque?

In order to answer this question, some details need to be considered. If the poor are badly in need of financial help and do not beg others so people are not aware of their state, which is the case of those on whom you spend,thengiving them charity is preferable over a donation in building the mosque. This is because the mosque will be built anyway, Allaah Willing, whereas no one is aware of the difficult situation of those poor families.

However, if the poor are not in a pressing need and there is no mosque in the neighborhood where you live or its construction depends on you, then in this case we can say that donating in building the mosque is preferable.

Allaah Knows best.